Given the current budgetary outlook in the US, I wouldn't be surprised in the least if it were implemented, but it is an incredibly foolish proposal. Requiring US citizens to get visas to visit EU countries would be even more foolish. Tourists and business visitors should be encouraged, not discouraged, plus the Eurpean emabassies and consulates in the US don't need the extra work of processing tons more visa requests.
I agree with you on that.
However, the US keep implementing more and more measures and requirements for visitors. The Visa Waiver Programme is a reciprical agreement designed to ease travel between countries. If one country starts implementing more and more restrictions and then also costs, then it is only natural that the other country will react in kind.
Reintroducing a visa requirement for US citizens is also the most effective way that the EU can put pressure on the US to rescind this - because the pressure will come from US citizens (their own voters) who then have to go through their own inconvenient and time-consuming process to travel as a direct consequence of this policy.